This invention relates to image sensor array systems for reading dataforms and, more specifically, to systems enabling oblique access to image data for efficient reading and decoding of obliquely oriented dataform images.
Images are commonly sensed in two-dimensional arrays of sensor cells utilizing photodiodes. In order to access image data (developed by conversion of incident radiation to charge or potential temporarily stored in individual sensor cells, for example) the entire array of sensors is typically scanned on a sequential line-by-line basis under the control of shift registers or other control circuitry.
While such arrangements may be suitable for sensing and reading out entire images, they are less efficient in accessing only a selected portion of an image. A disadvantage in speed of operation results from the need to read out an entire 1 to N lines of image data in order to provide access to selected image data which may exist at the Nth line. Thus, for example, for an image sensed by a 128xc3x97128 sensor array, access to a selected portion of image data, such as line 120, a particular pixel in line 120, or lines 120-128, will require that image data at lines 1-119 first be read out and discarded. While the actual time required to read out such 119 lines of unwanted image data may be of short duration, the total wasted time may be significant in repetitive operation of a high-speed system. Alternatively, acceptable operating time may be achievable, but may necessitate the higher cost of very high speed circuits (e.g., high capability integrated circuits).
The automated reading of bar codes and matrix codes provides one example of an operative need for access to image data for only a portion of an image. An automated system may scan an image area which includes a two-dimensional bar code, for example. The location of the bar code within the image area can then be determined as described in U.S. Pat. No. 5,304,787, entitled xe2x80x9cLOCATING 2-D BAR CODESxe2x80x9d, issued Apr. 19, 1994, the content of which is hereby incorporated by reference. With information as to the actual location of the bar code within the image area, it is then desirable to be able to access the limited area bar code image data without the necessity of reading out image data for the entire image area.
Even with information as to the location of a bar code, a bar code obliquely oriented in an image area would typically be read out on a horizontal line by line basis. As will be discussed, horizontal line (or vertical line) readout applied to lines of bar code elements which are obliquely oriented provides less than optimum readout efficiency.
Prior image sensing systems operating with line-by-line sequential readout of image data can be provided in a variety of embodiments. For example, an integrated circuit approach is described in international application number WO91/04633, published under the Patent Cooperation Treaty on Apr. 4, 1992, entitled xe2x80x9cI.C. Sensorxe2x80x9d. This publication illustrates an integrated arrangement of a sensor array and charge sampling devices enabling readout of image data for an entire image, but not randomly accessed portions of the image.
A number of image data readout variations, including arrangements employing random addressing and superpixel readout for readout of different image areas at different resolutions to achieve increased frame rates, are described in U.S. Pat. No. 5,262,871, entitled xe2x80x9cMULTIPLE RESOLUTION IMAGE SENSORxe2x80x9d, issued Nov. 16, 1993. Also, U.S. Pat. No. 5,396,054, entitled xe2x80x9cBAR CODE READER USING SCANNED MEMORY ARRAYxe2x80x9d, issued Mar. 7, 1995, addresses scanning a memory to determine the position, size and shape of a stored bar code image in order to define the angular displacement of rows of bar code elements. However, these references do not disclose effective arrangements for implementing oblique access to image data or the provision of address signals for efficient reading of oblique line components of image data.
Objects of the present invention are, therefore, to provide new and improved image sensor array systems, and such systems enabling access on an oblique line basis to more selected portions of image data sensed by an image sensor array.
An additional object is to enable reading of an obliquely oriented bar code along oblique lines transverse to individual bar elements of the bar code.
In accordance with the invention, an oblique access system, enabling access to dataform image data via an oblique line component of an image portion containing an image of the dataform, includes a two-dimensional array of image sensor cells positioned in rows and columns and arranged to provide image data representative of an image area including the image portion containing the dataform image. An address unit is arranged to provide address signals effective to identify a stepped pixel pattern of sensor cells representative of the oblique line component, the oblique line component being positioned obliquely to the rows and columns of the array. The address signals are provided in a form usable to access image data originating from sensor cells comprising the stepped pixel pattern. A data access arrangement responsive to the address signals is arranged to make available for further use output signals representative of image data originating from sensor cells comprising the stepped pixel pattern. The output signals are representative of the oblique line component of the selected portion containing the dataform image.
The oblique access system as described thus provides the output signals as a one-dimensional sequence of image data values without related information to identify the two-dimensional oblique orientation of the oblique line component. As a result, the output signals effectively represent the oblique line component after rotation to a row or column alignment not oblique to the rows and columns of the array of image sensor cells.
An oblique access method for accessing image data representative of a dataform, includes the steps of:
(a) providing image data representative of rows and columns of pixels comprising an image area including an image portion containing an image of the dataform;
(b) providing address signals identifying a stepped pixel pattern representative of a first oblique line component of the image portion which is positioned obliquely to the rows and columns of pixels;
(c) utilizing the address signals to make available for further use output signals representative of image data for pixels included in the stepped pixel pattern and thereby representative of the first oblique line component of the selected image portion containing the dataform image; and
(d) utilizing the output signals to decode the dataform.
For a better understanding of the invention, together with other and further objects, reference is made to the accompanying drawings and the scope of the invention will be pointed out in the accompanying claims.